DC Question

[NWSanta]

Help....

 

Trying to figure out why my CMB16 Keeps taking out my 12 Volt Power Supplies?

 

I bought these.

 

LED Light strips.

 

Last month and I've been able to make them work great with my show and the controller flashes them on and off and changes colour as expected. I'm feeding them with a DC 12 Volt 2 Amp power brick but, it only lasts about a week and then quits. I changed it out with a different one with the same result.

Am I simply drawing more than what the brick can put out? 

From my Math these strings are 72 Watts each and I'm running 6 of them 3 x 2 strings together.

So I'm thinking I must need a 36A power supply to keep up with the demand of these LEDs?

 

Does that make sense or am I missing something?

 

Let me know at your convenience guys!

 

Evan

 

[Grinch]

Yes you need a larger power supply.  36A is the correct number mathematically correct but you also need reserve so go bigger

[k6ccc]

Yep, those are 72 watt strips (when full on).  72 watts at 12 volts is 6 amps per strip and you have 6 of them so your are correct that totals 36 amps.  You need a far larger power supply (or two).  I'm surprised that the supply lasted more than a minute or two and I doubt it was lighting those strips worth a darn before dying.  Even the common 350 watt power supplies many of us run from Ray Wu's store on Alibaba are not big enough without having two of them (at least if you run full white very much).

 

The other thing you need to be careful of is current capacity of the board.  Assuming you have 2nd generation boards (metal tabs on the transistors rather than plastic tabs), each channel can handle 4 amps, with a 20 amp max per 8 channel bank.  A 72 watt strip is about 2 amps per color, so you probably could get away with 2 strips for each group of three channels.  If I am reading what you are trying to do, I understand that you have 3 groups of two strips each.  To keep the amp limits under control (assuming a single CMB16 card, I would do something like this:

 

8  Strips 1 & 2 Red

7  Strips 1 & 2 Green

6  Strips 1 & 2 Blue

5  Strip 3 Red

4  Strip 3 Green

3  Strip 3 Blue

12  Strip 4 Red

13  Strip 4 Green

14  Strip 4 Blue

9  Strips 5 & 6 Red

10 Strips 5 & 6 Green

11 Strips 5 & 6 Blue

 

This assumes strips 1 & 2, and strips 5 & 6 are running the same programming.  It does allow strips 3 & 4 to be the same by programming it that way in sequencing.  I had to split one of the pairs of strips in order to keep the total power on each bank to less than 20 amps.   Now, in case you are wondering why the slightly odd order, the 6 outputs with 2 strips on them are physically closer to the power input connectors on the card so it reduces heat generation and voltage drop in the traces on the card.   OK, I'm being a little picky on the last part, but thinking about stuff like that is part of my job.

I would then likely get two of the 350W power supplies from Ray Wu and have one power supply powering each side of the board.  Also, don't plan on putting much of anything else on that board (even though there are unused channels).

[NWSanta]

The stuff you learn!!! 

 

I had no idea that's what those lights were drawing. I guess in my head I was just thinking these are little LEDs they won't draw that much. Each arch has a little less than two strips on it as I i knocked about 3 feet off each one as they were too long for my arches. 

Each channel only has one colour on it.(x 2 strips)

 

So I will purchase two power supplies from Ray and look locally to see what I can find. I don't think Ray's power supplies will get here in time for the whole season. 

Maybe somewhere locally will have something?

 

Thanks for all the information and tips!!!

 

Evan

[k6ccc]

The stuff you learn!!! 

 

I had no idea that's what those lights were drawing. I guess in my head I was just thinking these are little LEDs they won't draw that much. Each arch has a little less than two strips on it as I i knocked about 3 feet off each one as they were too long for my arches. 

Each channel only has one colour on it.(x 2 strips)

 

 

Each LED doesn't take much power, but you have 900 of them per strip, so it adds up fast.

And before you say there are only 300 per strip, remember that a single RGB LED looks like a single LED, it's really 3 separate LEDs on a single die.

[NWSanta]

Each LED doesn't take much power, but you have 900 of them per strip, so it adds up fast.

And before you say there are only 300 per strip, remember that a single RGB LED looks like a single LED, it's really 3 separate LEDs on a single die.

 

Yup, RGB Newb mistake #1 of many to follow this year I'm sure!

 

Thanks for your help!